Penghu Islands are surrounded by the seahave good conditions for the development of coral reefs. There are coral reefs of different sizes outside the seashores of each islet. However, when the sea temperaturesalinity change,when the coral is exposed out of the sea for a long time, it will die. After the dead coral reefs are broken by the windwaves, they are gradually transported around the isletsdeposited on the seabedformed by the cementation of calcium carbonate over the years. So, beach rock is a special beach landscape caused by biological deposits cemented by calcium carbonateseashore sediments of non-biological debris. Most of these rocks are distributed in the places where the islets have sandy beaches. The largest ones are seen on the north shore of Zhuwan, the east side of Beiliao,the south of Jibei Port. These beach rocks are mainly sandygranular. Except for a little basalt debris, they are mainly composed of silica sand, coral detritus, seashell fragmentsforaminifera shells, which are cemented by calcium carbonate. Residents often dig this rock out to build windbreaks for vegetable gardens. The specimens collected by this center are from Qitou Village, Paisha Township.